This looks to be due to r10088, which changed:
self.nesting_level += 1
mod = __import__(app_name, {}, {}, ['models'])
self.nesting_level -= 1
if not hasattr(mod, 'models'):
to:
self.nesting_level += 1
try:
models = import_module('.models', app_name)
except ImportError:
self.nesting_level -= 1
in django/db/models/loading.py
The new code's try/except ImportError is not equivalent to the old code's testing if the returned mod has a 'models' attribute, as the new code now swallows import errors that the old code used to raise.
I have no idea how to fix it, though, since I don't know what would be equivalent to what the old code did when using the new import_module.